Automatic carriage control for duplicating machines



E. L. WALL Jul 's, 1935.

AUTOMATIC CARRIAGE CONTROL FOR DUPLICATING MACHINES -Fi 1'ed Nov. 2, 1 932 2 Sheets-Sheet 1 INVENTOR EL. PVall,

BY ATTORNEY E. L. WALL July 9, 1935.

2 Sheis-Sheet 2 Filed Nov. 2, 1932 INVENTOR EL. u a-zz, BY

, ATTORNEY I v V MN a 9 MNN D Patented July 9, 1935 AUTOMATIC CARRIAGE CONTROL FOR DUPLICATING MACHINES Edmund Leo wan, Detroit, Mich., assignor, by

iil'ilesne assignments, to R. W. Glasner, Chicago,

Application November 2, 1932, Serial No. 640,887

6 Claims, (01. 90-135) This invention relates to improvements in duplicating or milling machines, more particularly to improvements in the control of the carriage on which the tracing, cutting and other mechanism ismounted, and its objects are as follows:

First,'to cause the so-callcd tool carriage to move across the work at either a substantially uniform rate or at a variable rate or at combinations of said rates, in other words, at a pace harmonizing with a given'profile of the pattern or master so that when the tracer either drops into a cavity or rides upon an eminence the carriage will be slowed and even stopped, and that when the tracer traverses a substantially uniform profile as to high and low places the carriage will proceed at a substantially uniform rate, but to allow 'the cutter ample time in which to cut into the work and make a perfect reproduction.

Second, to employ the tracer mechanism as the means for controlling I the longitudinal movements of the tool carriage along the work as well as the transverse movements of the cutter into and out of the work.

Third, to combine a governor valve device with the tracer of a hydraulically operated milling mechanism, said device being automatically operative by the volume of fluid'which said mechanism permits the passage of. v

Fourth, to provide a governor valve device which is responsive to a fluid flow in either directionin the pressure line, thereby to throttle the flow of fluid to the so-called driver cylinder when the tracer either drops intoa cavity or sur-' mounts an eminence, thereby either slowing or stopping the tool carriage.

Fifth, to couple the tracer mechanism and governor valve device in series in the pressure line, the respective structures being such that when there is an excess passage of fluid through the governor device, said device will operate to cut down the flow to the driver cylinder and slow the tool carriage, and when the passage of fluid through said device diminishes it will increase the flow to the driver cylinder and speed up the tool carriage. I

Other objects and. advantages will appear in the following description, reference being had to the accompanying drawings in which Figure 1 is a diagrammatic view of the tracer and cutter mechanism which is mounted on a carriage, the view being divided on the lines A, B so as to avoid confusion by the diverse movements involved, the tracer and cutter mechanism above the line A being movable in and out with respect to the pattern and work or, in other words, transversely of the machine, the carriage below the line B being movable longitudinally of the machine or, in other words back and forth in front of thework.

Figure 2 is a longitudinal section of the governor valve device, constituting the present invention, and the tracer cylinder with which it immediately cooperates.

Figure 3 is a cross section taken on the line 33 of Figure 2, particularly illustrating the medial annulus and disc valve.

Figure 4 is a cross section taken on the line 4-4 of Figure 2 illustrating another valve.

Figure 5 is a sectional view of the driver cylinder and its related driver piston.

The fundamental purpose of the invention is to automatically control the movement of a tool carriage in a duplicating machine during the act of reproducin a pattern, the control working in such a way that the carriage will not necessarily move back and forth with a uniform motion or, at a uniform rate of speed, but rather will adaptitself in terms of motion, so to speak, to the particular profile of the pattern being traversed at the time by the tracer. The effect of the control is toslow, stop, speed up and diminish the speed of the carriage to suitthe foregoing profile so that the cutter will have ample time in which to perform its cutting operation and will not turn out an imperfect'reproduction by virtue of being forced to travel with the tool carriage at a uniform rate of speed.

It will be apparent that" when the tracer drops into a cavity or reaches a' virtually perpendicular wall of an eminence which it must surmount, there must be time for thecutter to reproduce the respective cavity and eminence in the work, audit will take more time to make these reproductions than would be required in reproducing relatively small low and high places. The governor valve device is therefore made to work automatically on the tool carriage so that the movements of the latter will correspond with the requirements of the cutter.

While the governor valve device isapplicable to pressure fluid operated duplicating machines in general, it is particularly adapted to the duplicating machine of Edmund L. Wall, disclosed in an application filed February 26, 1931, Serial No. 518,528. The instant drawings are based on the drawings in that application, but only such parts of the structure are shown herein as are directly concerned with the invention. In other words, only enough of the structure of the co-pending application is herein shown in combination with the governor valve device to make the operative assemblage.

In order that the principle of the co-pending application may be understood, attention is directed to the following descriptionz-The foundation of the machine comprises a stationary table I (Fig. 1') which is supported above the floor by legs 2. The table'flxedly carries a rail structure 3'. Right and left stops 6, 1 are associated with the table v These stops are adjustable in accordance with the length of a pattern or master 6 which is intended to be traced for reproduction in the work 9. The pattern 8 is to be regarded as a rela-- tively soft material such as plaster of Paris, while the work 8 may be regarded as of a relatively hard substance such as metal. The pattern Band work 6 are stationary along the table I. In factv they may be supported on the table by means not shown.

The manner in which the pattern 8 (Fig. l) is traced is as follows:--A tracer |4 (Figs. 1 and 2) is made to hear at its point on the surface of the pattern by a spring I5 which is adjustable by means of a barrel |6 with respect to a cylinder I! so as to press on the assemblage ahead of it in the cylinder with varying degrees of pressure and thereby cause the tracer M to bear on the pattern 8 correspondingly.

Considerable radial motion will occur in the tracer l4 and in a shank 20 by which the tracer is carried. The radial motions as well as a rectilinear inward motion of the tracer M will be transmitted to a sleeve 23 which carries a circular valve plate 24. The sleeve includes piston components 2|, 22. This plate occupies a chamber 25, and it is against one edge 26 of this chamber that the valve plate 24 seats under the influence of the spring IE to cut off the flow of pressure fluid through the cylinder -|8. The edge 26 is, therefore, a valve seat.

An inlet 21 communicates with the chamber 25. Pressure fluidis introduced into the cylinder i8 between the piston components 2|, 22 upon the least unseating of the valve plate 24. Such unseating will occur during the foregoing move-.

ments of the tracer H as the latter traverses a given profile of the work 8. A fluid outlet 28 communicates with the cylinder l8 on the right side or the piston component 2|. The sleeve 23 has an opening 32, and it is through this opening that a passageway for the fluid is completed between the inlet 21 and outlet. when the sleeve is shifted by the motions of the tracer |4, these motions being imparted to the rim of a cup 33 on the cylinder, against which rim a disc 34 on the inner end of the shank 20 has bearing.

In tracing the pattern 8 the tracer I4 is as likely to suddenly encounter a high place as it is to drop into a cavity.- In the first instance the tracer 4 may either rock or partake of a bodily inward movement, either resulting in a movement oi! the sleeve 23 toward the right as indicated by arrow a. The unseating of the valve plate 24 permits a flow of pressure fluid as previously stated. Upon encountering a cavity the tracer M will drop in, being compelled to do so as later brought out.

The manner in which the cutter is made to keep pace with the tracer I4 is as follows:--The cutter 39 (Fig. 1) may be regarded as 01' any type suitable to remove material from the work 9. The jaws of a chuck 40 are operated by a draw bar (not shown) which extends along a hollow spindle .42 at the free end or which there is a head. 43. This head is on the draw bar, and by turning the head the draw bar is operated to open and close the chuck.

, Bearings 45, 46 (Fig. 1)v support the spindle 42 which is revolved therein by a bevel gear 41. This gear is swivelly supported by a third bearing 46. A longitudinal keyway 62 in the spindle 42 receives a key (not shown) inthe hub 01' the gear 41. The gear 41 remains relatively sationary, and it revolves the spindle 42 as the spindle is shifted back and forth.

'The gear 41 is driven from the pulley l4 0! a motor 66 by means of a beit connection which transmits the power to a speed reducer 66. This reducer drives gear and shaft connections commonly designated 51, it being noted in Figure 1 that the last gear 61 of the series drives the bevel gear 41.

A cylinder 58 (Fig. 1) has a single fluid opening 59 with which one end of a conduit 64 is connected. This conduit is part or a pressure fluid system, and pressure fluid is adapted to flow into it in either direction, either into the cylinder 62 01' out of it. The other end of the conduit is connected with a governor valve device G which is the principal subject of this application. The fluid system will presently be traced through the governor device as it has been through the cylinder la, the outlet 22 of the latter having a pipe connection 6| with a sump 62 or any description. The pipe 6| is one of the exhaust pipes for the pressure fluid system. The sump 62 is usually stationary, and the exhaust pipe simply travels over the sump.

The cylinder 58 is identified as the cutter cylin der by virtue of its association with the cutter II. It has a piston 64 which reciprocates the spindle 42 by means oi a yoke 65. Fluid under pressure introduced into the cutter cylinder 52 keeps the cutter 39 against the work 2. A diminution of the fluid pressure relaxes the pressure 01' the cutter 39 so that the latter may recede from the work.

Pressure in the fluid system is derived from a pump 61 which recirculates the fluid in the sump 62. The pump discharges into a main pipe stand 68. In the event the pump 61 is stationarily mounted with respect to the sump 62, the pipe stand will include a flexible section 66. A branch 69 of the pipe 62 supplies the cylinder II and governor device G with pressure fluid. A valve 16 in this branch, enables the regulation of the pump pressure in the conduit 62 and consequently in both cylinders I! and 56. Pressure fluid may flow either through the governor G into the pipe 60 and so into the cutter cylinder 66 to drive the piston 64 to the left and keep the cutter 39 held against the work, or it may flow through the cylinder |8 into the discharge pipe 6| thus relaxing the pressure in the pipe 60 and cylinder 62, permitting the cutter 39 to recede from the work.

The lowest normal plane which the tracer I4 is supposed to reach is denoted 1| (Fig. 1). Recession of the tracer from this plane or from any low place which it may occupy occurs indirectly by means of a weight 12. This weight is permitted to function only when a movement of the tracer I4 causes an opening'oi the valve plate 24 (Fig. 2) and a consequent pressure drop in the conduit 46. The weight 12 has a cable connection 13 with a slide plate 14. This plate carries the bearings 45, 46 and provides the support for the cylinder l8 and governor device G so that all of these parts move as one with the slide plate 14.

A longitudinally movable carriage 11, usually longitudinally slidable, carries the slide plate 14. The carriage 11 moves longitudinally on the rail structure 8 in front of the pattern 8 and work 9. The plate 14 slides transversely of the carriage 11 so that the tracer I4 and cutter 39 move in and out with respect to the pattern 8 and work 9.

The manner in which the carriage 11 is made to work back and forth is as follows:'-The carriage includes a head 88 (Figs. 1 and which is a part of it. This head has an attached rod 82 which carries a double headed piston 84 (Fig. 5). This piston is made to work back and forth in a driver cylinder 85. This cylinder is flxed on the table I, and as the piston 84 is made to work back and forth the carriage 11 and all of its superimposed parts are made to traverse the rail structure 8 longitudinally in front of the pattern 8 and work 9.

sure for the operation of the piston 84. This branch pipe is controlled by the governor G. The pressure fluid of the branch pipe is delivered to a trip valve the details of .which are omitted. It is suflicient to say that this trip valve is contained by a casing 88 forming part of the carriage 11..

The stem 9| of the trip valve loosely carries a tripper 92. This tripper is engageable'with the stops 6, 1 (Fig. 1) when the carriage 11 nears the end of its movements, thus turning the trip valve to new positions and causing the automatic reversal of the carriage 11.

This trip valve controls right and left passages 85, 96 in the head 80 (Fig. 5) so that when the valve is in one position pressure fluid will 'flow into one of the passages and out of the other passage. These passages terminate at opposite sides of thedouble headed piston 84 and consequently with opposite ends of the driver cylinder 85. The present setting of the trip valve affords communication of the branch pipe 86 with the passage 95 so that pressure fluid is admitted to the left .end of the cylinder 85. Pressure at the left side of the piston 84 drives this to the right (arrow c, Fig. 5), consequently movingthe carriage 11 'to'the right (arrow d, Fig. 1). The same setting of the trip valve permits an exhaust of fluid from the right end of cylinder 85 through the passage 96 to a second exhaust pipe- I I2. This pipe discharges into the sump 62.

In actual practice provision is made for spacing the tracer I4 and cutter 39 in the vertical direction at the end of each right and left movement of the carriage 11. Usually this spacing is in the downward direction. The mechanism for accomplishing this spacing is fully disclosed in the co-pending application but is omitted here because it has no bearingon the present invention which comprises the governor valve device G. A base I58 (Fig. 2) carries structure forming fluid chambers I54, I55. The first of these has a medial annulus I56 which provides a loose seat for a valve I51 in this respect: -The valve I 51 consists of a disc which is movable through the annulus I56 from its. neutral position within the annulus, this movement necessitating a clearance of several thousandths of an inch between the confronting faces of the annulus and disc.

The pressure conduit 66 communicates with the chamber I54 at the left of the annulus I56. An

of the stem adjacent to the valve are supported closure for the chamber I54.

An enlargement I64 of the stem I60 has an annular groove I65 providing a valve in the fluid chamber I55. The enlargement I64 is slidable in the chamber I55 and its valve I65 controls a port I66 with the opposite ends'of which the respective main pipe stand 68 and branch pipe 86 are connected. Glands I61 keep packings at the ends of the chamber I55 under'pressure so as to prevent leakage around the enlargement I64.

Springs I68, I69 act on the stem I68 to maintain the neutral position of the valves I51, I65.

' The outer ends of these springs engage abutments A branch'pipe 86 delivers fluid at pump presbase I53. The innerends of the springs engage washers I12, I13 which abut the shouldered ends of a the enlargement I64. The enlargement is as long as the chamber I55, and. presuming the springs I68. I68 to be equalized their effect is to center the enlargement I64 in the chamber I55 and consequently station the valve I51 withinthe annulus I56.

The operation is readily. understood. In considering diagrammatic Figure 1 it must be-remembered that the structure above the line A works at right angles to the structure below the line B. The carriage 11 moves back and forth on the track structure 3 in front of the pattern 8 and work 9 which are supposed to be lying in theplane of the paper. The tracer I4 and cutter 39 would then be working into the paper, so to speak, but rather than to disclose the parts in correct relationship, which would mean an unsatisfactory been adopted, relying on the reader'sunderstand- ,ing that the two parts work at angles to each other.

As long as the pump 61 is in operation there is positive pressure in the flexible section 68, pipe. stand 68 and its branch 69. Consider the governor device G as in its neutral position (Fig. 2). Fluid at pump pressure will flow from the pipe stand 68 with undiminished force through the port I66 (Fig. 2) and from there through the branch pipe 86 down to the trip valve in the casing 88. The trip valve is now directing the pressure fluid into the left end of the driver cylinder 85 by way of the'passage 95, the fluid in the right end of the cylinder exhausting through the passage 96 and exhaust pipe I I2 into the sump 62. As long as pressure fluid is being supplied to the driver cylinder 85 the carriage 11 will 'bemoving back and forth, its reversal occurring by means of the tripper 92 and stops 6,1 as previously pointed out. As long as the valve I65 of the-governor G (Fig. 2) remains in the mid or neutral position with respect to the port I66 the carriage 11 will, be propelled back and forth at a uniform rate.

Still considering the same neutral position of the governor valve device G (Fig. 2) fluid at pump pressure will be present in the cutter cylinder 58 (Fig. 1) by virtue of a'very slight passage of fluid from the branch 69 (Fig. 1) into the right end of the fluid chamber I54, through' the space between I56 and I51 and into the conduit 68. This passage of fluid is only suflicient to cause a very slight movement of the piston 64 (Fig. 1) to the left, but the pressure is sufficient to keep the cutter 39 up to its work. The annular space between I56 and I51 (Fig. 2) enables this passage of fluid without hindering the action of the springs that neutralization is established both as to the valve disc I61 and the valve I66.

At this particular time the large volume of the pump output goes through the port I66 (Fig. 2) past the valve I66, the latter being in the wide open or neutral position as stated above. A relatively small volume of the fluid goes through the space between I56 and I5I. The resistance at this point is consequently low, and the springs I69, I69 are able to neutralize the valve assemblage.

As long as the tracer I4 traverses relatively small lowand high places along a particular line of profile of the pattern 9 the tracer I4 and cutter 39 will simply fall and rise without any i at change in the motion of the carriage 'II (Fig. 1). Imagine the tracer as traversing a surface such as just described, or a surface which is substantially flat and straight. Under this condition there is no need of increasing or decreasing the amount of fluid in the cylinder 59 (Fig. 1). The tracer valve or circular valve plate 24 (Fig. 2) will be spaced a short distance from its seat 26 as it must be in order to provide an outlet for the relatively low but constant volume of fluid delivered from the branch 69 and valve 10.

In the event the tracer I4 reaches a'slight concavity it will follow the surface of the concavity by virtue of the constant pump pressure behind the piston 64 (Fig. l) and the cutter 39 will cut a corresponding concavity forthe same reason. It is true that the pressure in the cutter cylinder 59 is expended directly on the cutter 39, but inasmuch as the tracer I4 is carried by the slide I4 in common with the hangings of the cutterit follows that the tracer and cutter will partake ofvirtually simultaneous in and out movements.

In the event of the tracer I4 riding upon a high place, the momentary backward displacement of the tracer, whether that be directly inward with respect to the cylinder I6 (Fig. 2) or merely a rocking motion, will shift the sleeve 23 to the right (arrow and open the valve 24 to a greater extent than it was before. Thus a wider opening of the valve 24 lets more of the fluid through into the exhaust pipe 6| (Fig. 1). There isa diminution of the pressure in the conduit 60 because of the diversion of more of the fluid from the right end of the chamber I54 (Fig. 2)

The foregoing diminution in pressure in the line 66 is felt in the cutter cylinder 59. weight I2 pulls back on the slide plate I4 until the piston 64 is resisted, the permissible amount of pulling back agreeing with the high place which the tracer I4 has ridden. The higher place will be reproduced in the work by the cutter 29. So far the operation is practically identical with the operation of the mechanism in the copending application. The specific arrangement (the governor valve device G) takes care of instances where the pattern 9 has very pronounced cavities and eminences which take more time to traverse than ordinary low andhigh places, consequently making it necessary to slow the carriage II in order that the cutter 39 may have time to conformably shape the work.

Consider the tracer I4 as having reached a deep concavity. The condition will be as though the tracer were about to drop into a hole, so to speak. The tracer should drop into the hole but the carriage I'I must be slowed in order to give the tracer time to drop into the hole and, what, is more important, give the cutter 99 time to reproduce the hole in the work I.

The.

I66, I69Tthese then so positioning the stem I60 Since there is now a hole in front of the tracer I4 the tracer ceases to bear hard on the pattern. The valve 24 (Fig. 2) closes on its seat 26. Instead of the fluid being diverted from the chamber I54 through the cylinder I8 (Fig. l) to the sump 62 as it was before, all of the fluid in the branch 69 goes into the chamber I54.

A pressure higher than usual is imposed on the right side of the valve disc I51. The space between I56 and I'I is insufllcient for the escape of the heavier volume of fluid. As a result the valve I5'I is forced to the left so as to let the surplus through into the conduit 60 and into the right end of the cutter cylinder 58 (Fig. 1). The cutter I9 is driven into the work with added force. At the same time the leftward movement of the valve I51 and its carried assemblage throttles the port I66 by virtue of the valve I65 moving leftward. The amount of fluid delivered to the casing 86 (Fig. l) is cut down. This slows the carriage 11 while the cutter 99 is made togwork harder.

The effect of the foregoing operation is to cause the cutter 39 to cut deeper into the work. When the tracer I4 reaches the bottom of the hole it will bear on the bottom and cause an outward displacement of the valve 24 (Fig. 2). This again diverts the fluid from the chamber I54. The former condition is restored, namely the neutralization of the valve I51 and its carried parts. The tracer I4 and cutter 99 will progress in the new position until the next change in the pattern occurs.

Suppose this change to be a very high place; an up going wall as steep as the down going wall was supposed to be. Both the tracer and cutter will need time to negotiate this wall, and the carrier 11 must again be slowed to provide time. The first effect will be a lateral motion of the tracer I4. This opens the valve 24 (Fig. 2).

There will be a discharge of fluid through the the main eifect will be a surmounting 'of the I eminence by thetracer. There will be a considerable inward displacement of the tracer and, an opening wide of the valve 24 so that there will be a heavy discharge of fluid at pump pressure through the tracer cylinder I8 to the discharge I pipe 6I, and a consequently heavy discharge of fluid from the cutter cylinder 58 to the conduit 60 because of the action of the weight I2.

This heavy discharge from the conduit 69 now occurring from left to right in the chamber I54 (Fig. 2) will displace the valve I51 to the right of the annulus I56, letting the fluid through, and at the same time displacing the valve I65, either partially or wholly closing the port I66. A partial closure of this port will diminish the supply of fluid to the driver cylinder with a consequent slowing of the carriage TI as before, while a total closure will cut off the supply entirely with a consequent stopping of the carriage I1.

As soon as the tracer I4 surmounts either a high place or reaches the level of a low place the normal condition of the machine will be restored. The governor valve device G will reassume its neutral position, and that position will be maintained until there is again a sudden passage'ot fluid through the chamber I64 in either direction. It is always the passage of an excess of fluid in either direction which displaces the valve I51 and causes a partial or total closure of the valve I65.

It will be understoodthat the neutral position of the valve I6! is maintained by the Springs I68, I69. A movement of the stem I60 toward the left will place the spring I68 under tension, while a movement toward the right will place the spring I69 under tension. When the condition causing the displacement is removed, either spring will act on the enlargement I64 to return the valve assemblage to the place where it started from.

I claim:

1. In a milling machine, a movable carriage and a movable cutter carried by said carriage, a master fixedly supported with respect to said carriage, a pressure fluid system including actuating means which is actuated by force of the pressure to move the carriage along the master, by-pass means in a portion of said system, said by-pass means being operable by a relatively heavy surge of fluid therein, and a valve controlling another portion of said system, sad valve being moved by the operation of said by-pass means to throttle the flow in said other portion of the system, and therebythe volume delivered to said actuating means.

2. In a milling machine, a movable carriage and a movable cutter carried by said carriage, a master fixedly supported with respect to said carriage, a pressure fluid system including actuating means which is actuated by force of the pressure to move the carriage along the master, a tracer to follow the contour of said master, said tracer being movable by virtue of ,its encountering unevenness in the contour of the master, by-pass means in a portion of said system being operable by an abnormally heavy surge offluid in said portion when the tracer encounters an abrupt formation in said contour, and a valve device in another portion-of said system directly supplying said actuating means, said valve device being moved by operation of said by-pass means to throttle the flow to said, actuating means and thereby vary the rate of movement of said carriage.

3. In a milling machine, a fixedly supported master, a movable carriage and a driver cylinder having a piston to move the carriage along the master, a movable cutter carried by the carriage and a cutter cylinder having a piston for keeping the cutter up to its work, a pressure fluid system supplying both cylinders to expend pressure against the respective pistons, a tracer to follow the master, being movable by the unevenness thereof, a valve device in a part of said system subject to minor openings by the tracer for a minor exhaust of fluid from said cutter cylinder and a relaxation of the pressure against its piston, by-pass meansin the adjacent portion of with respect to a fixed master, a movable work cutter carried by the carriage, means tending to pull the cutter away from the work, pressure fluid apparatus resisting said means and tending to pull the cutter toward the work, said apparatus including a pressure fluid system embracing said actuating means, a tracer coupled with the cutter having vibratory motion in reference to the cutter, a valve in said system being subject to the vibrations of the tracer to increase and decrease the effectiveness of said apparatus, hence decrease and increase the effectiveness of the pusher means, by-pass means producing a consonantly large opening in said system by a large opening of the valve when the tracer encounters an abnormally high place, and a valve in that portion of the system supplying the actuating means, being operated by the by-pass means to throttle the flow to said actuating means and correspondingly slow the carriage.

5. In a milling machine, a governor for controlling the movable tool carriage thereof, said governor comprising two fluid chambers, a'pressure fluid system having branches embracing each of the chambers, a valve in one of the chambers being disposed across the inlet and outlet of the respective branch and thereby subject to movement upon a surge of fluid in said branch through the respective chamber, a valve in the other chamber, and means connecting the valves so that said movement will throttle the fluid flow in said other 'chamber.

6. In a milling machine, a governor for controlling the movable tool carriage thereof, said governor comprising two fluid chambers, a pressure fluid system for actuating the carriage, including branches each of which has an inlet and an outlet at the respective chambers, an annulus in one of the chambers situated medially of the inlet and outlet, a valve disc peripherally spaced from the internal circumference of said annulus,

a stem carrying said valve disc, said stem having ,ized position with respect to the annulus and said valve in a fully open position with respect to its inlet and outlet.

EDMUND LEO WALL. 

